1. Field of the Invention
The present invention relates generally to a light source device, and more particularly to a light source device without additional light control elements.
2. Description of Related Art
Along with the development of semiconductor fabrication process technologies, micro-sized luminous elements can be obtained by connecting light emitting diode (LED) dies to external pins and packaging them so as to replace conventional incandescent lamps. As the luminous elements have advantages of long life, low power consumption, high light emitting efficiency and a richer color gamut, they have been widely applied. However, as the luminous intensity of a single luminous element of an LED is not sufficient, a light source device generally comprises a plurality of LEDs so as to obtain sufficient luminous intensity. Moreover, since LEDs are directional light sources, LEDs can be obliquely arranged in a light source device, or a light control element can be selectively disposed in the light source device, so as to satisfy a user's light distribution requirement. However, on the one hand, obliquely arranged LEDs increase the mold manufacturing cost and assembly cost. On the other hand, the use of a light control element, such as a light control film, a geometric reflection screen, a deflection lens and so on, decreases the light-emitting efficiency of the light source device. As a result, the number of LEDs incorporated needs to be increased, which accordingly increases the cost of the light source device.
US patent application Publication No. 20060139933 discloses a light fixture called a luminaire with a reflector of negative focal length, wherein the luminaire screen comprises a reflector of negative focal length disposed at the top thereof and a side screen disposed at two sides thereof. Thus, upward incident light rays emitted from the light source are first reflected to the side screen by the reflector of negative focal length and then are further reflected such that a plurality of concentrated rays is formed. The emitted rays are emitted out at large angles for reducing glare, and, also, the design allows the height of the luminaire to be reduced.
As shown in FIG. 1, US patent application Publication No. 20060232976 discloses a light source device 1, which comprises a luminous element 10, a reflecting screen 11 disposed at one side of the luminous element 10, a light transmission portion 12 disposed at an opposed side of the luminous element 10, and a light diffusion portion 13 disposed between the luminous element 10 and the light transmission portion 12. Therein, the reflecting screen 11 is an arc-shaped screen and one edge of the reflecting screen 11 is connected to the light transmission portion 12. Light rays emitted from the luminous element 10 are reflected in paths denoted by ‘S’ via the light reflecting screen and further uniformly transmitted through the light transmission portion 12, thereby improving the light-emitting efficiency of the light source device 1 and obtaining uniformly distributed illumination.
In detail, the light diffusion portion 13 is disposed at the light emitting end of the light source device 1. The light diffusion portion 13 comprises a plurality of light diffusion zones. Each surface of the light diffusion zones has a plurality of arrays of microstructures. By controlling distribution of the plurality of arrays of microstructures, the Gaussian distribution of the luminous element 10 can be improved while collimating the scattered light beams in the range of the light transmission portion 12 and diffusing the light beams emitted from the center of the luminous element 10 to the light transmission portion 12 so that not only the luminous efficiency of the light source device is enhanced, but also the uniformity of the luminance of the light source device is improved. But such a method increases the assembly cost. Meanwhile, the use of the reflecting screen 11, light transmission portion 12 and the light diffusion portion 13 not only increases the cost of the light source device 1, but also reduces the light-emitting efficiency of the light source device 1. As shown in FIG. 2, U.S. Pat. No. 5,838,247 discloses a light source device 2, which comprises a base body 20 having a carrier surface, a plurality of luminous elements 21 disposed on the carrier surface of the base body 20, and a reflecting portion 22 disposed in the base body 20 and inclined toward the base body 20, wherein the base body 20 is substantially cup shaped, the reflecting portion 20 is disposed at the bottom of the base body 20 and is substantially conical shaped or pyramid shaped, and the luminous elements 21 are disposed at the periphery of the reflecting portion 22. By adjusting the disposing angle of the luminous elements 21 relative to the base body and the tilt angle of the reflecting portion 22 relative to the base body, light rays of the luminous elements 21 can be concentrated for transmission. However, as the reflecting portion 22 is a plane and cannot be adjusted corresponding to the light emitting angle of the luminous elements 21, light rays generated by the luminous elements 21 cannot be completely reflected by the reflecting portion. Moreover, a large number of luminous elements 21 are needed according to the tilt angle of the reflecting portion 22, thus increasing the cost and volume of the light source device 2 and decreasing the flexibility of the shape of the light source device 2.
Further, the conventional planar LED die bonding process involves the following: using SMT (Surface Mount Technology) for die identification and positioning; transmitting related information to an X-Y-Z die capturing system for die transfer and positioning, wherein the X-Y-Z die capturing system has three degrees of freedom X, Y, Z; using a CCD image identification system for die identification and positioning, wherein the dies are transferred to position for dispensing through the X-Y-Z capturing system; and finally curing the system so as to fix the LED dies to the substrate. As the capturing system only has three degrees of freedom, an LED die can only be fixed to a planar substrate, which—due to its fixed structure—cannot meet users' light distribution curve requirements.
Therefore, a need exists to find a way to overcome the above-described drawbacks of the conventional light source devices.